add body option validation

Throw nice error about body option,
instead of `first argument must be a string or Buffer`
from http.

index.js

@@ -67,6 +67,10 @@ function got(url, opts, cb) {
 		throw new GotError('got can not be used as stream when options.json is used');
 	}
 
+	if (body && !(typeof body === 'string' || body instanceof Buffer || isStream.readable(body))) {
+		throw new GotError('options.body must be a ReadableStream, string or Buffer');
+	}
+
 	function get(url, opts, cb) {
 		var parsedUrl = urlLib.parse(prependHttp(url));
 		var fn = parsedUrl.protocol === 'https:' ? https : http;

test/test-error.js

@@ -33,6 +33,14 @@ tape('dns error message', function (t) {
 	});
 });
 
+tape('options.body error message', function (t) {
+	t.throws(function () {
+		got(s.url, {body: {}});
+	}, /options.body must be a ReadableStream, string or Buffer/);
+	t.end();
+});
+
+
 tape('cleanup', function (t) {
 	s.close();
 	t.end();